This invention relates to a shock absorber device for linearly decelerating a machine part by imposing a relatively constant force on the part over the stroke of the device.
Shock absorbers which force fluid through a restricted orifice to convert the kinetic energy of a moving part into an increase in the thermal energy of the fluid are commonly used on machines. In a typical installation, a machine tool or transfer arm is repetitively moving back and forth between separate operating positions and the movement of the tool or arm as it arrives at each position is cushioned and decelerated by a shock absorber positioned on the tool or arm or on the adjacent supporting structure.
Shock absorbers of this general type are available in several forms. In one form, commonly referred to as a threaded body shock absorber, the housing or body of the shock absorber is threaded throughout its entire length and the shock absorber is typically mounted by threading the body into a supporting plate or bracket. A shock absorber of this general type is shown, for example, in U.S. Pat. No. 4,690,255 assigned to the assignee of the present invention.
In another form of shock absorber, commonly called a fixed flange shock absorber, the housing of the shock absorber includes a cylindrical main body portion and a flange is secured to either the front or rear end of the main body portion. Shock absorbers of this type are typically mounted by the use of mounting screws passing through apertures in the mounting flange to secure the shock absorber to a plate or support structure. Shock absorbers of this general type are shown, for example, in U.S. Pat. Nos. 4,059,175, 4,133,415, 4,298,101, 4,321,987, 4,482,035, and 4,702,355, all assigned to the assignee of the present invention.
In another form of shock absorber, commonly called a primary shock absorber, the shock absorber body comprises a central main body portion and reduced diameter threaded portions at the front and rear ends of the housing. This type of shock absorber is either rear mounted by the sue of the reduced diameter threaded rear portion or front mounted by the use of the reduced diameter threaded front portion. A shock absorber of this general type is shown, for example, in U.S. Pat. No. 4,694,939, assigned to the assignee of the present invention.
Whereas each of the described shock absorber types has advantages with respect to the manner in which it is mounted, each type is also limited to specific mounting arrangements which may not satisfy all of the mounting requirements of a given user and which may therefore require that a large inventory of parts be carried by the manufacturer, distributor, or user in order to satisfy all of the possible mounting requirements of the user.
It has also become increasingly popular to provide some manner of stop device as an integral part of the shock absorber to ensure that the component being stopped ends up at the same point with each decelerating action, to ensure that the shock absorber does not bottom out internally at the end of the decelerating movement and to precisely position the piston of the shock absorber as it nears the end of its stroke to optimize the fluid flow through the metering orifices to achieve a desired performance characteristic. In this regard, each of the described types of shock absorbers is amenable to the use of an integral stop member in certain mounting situations but requires a complex stop member arrangement in other mounting installations.